1. Field of the Invention
The present invention relates, in general, to grid structures used for geographic referencing systems, and, in particular, to nesting grid structures for geographic referencing systems.
2. Related Art
U.S. Pat. No. 5,839,088 describes a geographic location referencing system entitled the World Geographic Referencing System (xe2x80x9cWGRSxe2x80x9d). The WGRS was developed by Go2 Systems, Inc. (xe2x80x9cGo2xe2x80x9d) of Irvine, Calif., the same assignee as the present invention. The WGRS has an addressing scheme that is determined using a number of pre-defined grids. An address for a geographical location may be determined by determining a grid corresponding to the geographical location, subdividing a cell of the grid into as many levels of hierarchically arranged sub-cells as necessary to obtain a desired addressing precision, associating each sub-cell with a sub-cell code, identifying each sub-cell with a hierarchical arrangement of codes, and appending to the name of the grid a hierarchical arrangement of codes corresponding to the geographical location. The inventors of the present invention recognized it is additionally desirable in a geographic location referencing system to nest regional grids and local city grids so that a geographical location may addressed with respect to a local city grid and/or a regional grid. Navigation with respect to local city grid addresses is desirable because a local frame of reference generally has more meaning to users, especially users that do most of their navigation in a local area or city. Navigation with respect to a regional grid address may be more desirable for users that travel more outside of their local area or city. Correlating two partially overlapping grids so that certain areal and point references are congruent at higher levels of precision provides significant advantages.
Accordingly, an aspect of the present invention involves the recognition that it would be desirable to nest local city grids with regional or district grids so that a geographical location may be identified with respect to a regional grid and/or one or more local city grids. It is anticipated that for most users of the WGRS described herein, the majority of use will be on a local level. Being able to identify a geographical location with reference to a local city grid localizes the geographic referencing system, making the geographic referencing system more meaningful to the user.
Another aspect of the invention involves a nested grid structure of a geographical referencing system. The nested grid structure includes one or more regional grids generally centered on one or more respective grid origins, each regional grid including a plurality of cells. One or more local cities are located at least partially within the one or more regional grids. One or more local city grids, each including a plurality of cells, are generally centered on one or more respective local city origins of the one or more local cities. At least some of the plurality of cells of the one or more local city grids directly overlap and coincide with at least some of the plurality of cells of the one or more regional grids to form a nested grid structure.
An additional aspect of the invention involves a method of creating a nested grid structure for a geographical referencing system. The method includes determining a regional origin for a regional; centering a regional grid for the region generally on the regional origin, the regional grid including a plurality of cells; determining a local city origin for a local city located at least partially within the regional grid; and positioning a local city grid including a plurality of cells so that the local city grid is generally centered on the local city origin and at least some of the plurality of cells of the local city grid directly overlap and coincide with at least some of the plurality of cells of the regional grid to form a nested grid structure.
A further aspect of the invention involves a method of addressing a geographical location using a local city grid. The method includes providing a geographical location; determining a local city grid corresponding to the geographical location, the local city grid having a plurality of grid cells, a local city grid origin having global coordinates defined in accordance with a known global referencing system, and a local city grid name; subdividing a cell corresponding to the geographical location into as many levels of hierarchically arranged sub-cells as necessary to obtain a desired addressing precision; associating each sub-cell with a sub-cell code; identifying each sub-cell with a hierarchical arrangement of codes; and addressing the geographical location with an address formed by appending to the name of the local city grid a hierarchical arrangement of codes corresponding to the geographical location.
A still further aspect of the invention involves a method of addressing a geographical location within overlapping geographical areas of a regional grid and a local city grid of a geographical referencing system. The method includes providing a first address of a geographical location in a first geographical area, the first address comprising a hierarchical arrangement of codes of a first pre-defined grid corresponding to the first geographical area appended to the name of the first grid, the first grid being either a regional grid or a local city grid; determining a second pre-defined grid which corresponds to a second geographical area, the second geographical area having a portion which overlaps at least in part the first geographical area, the geographical location being within the overlapping portion, the second pre-defined grid being the opposite of the first predefined grid, either a regional grid or a local city grid; determining a hierarchical arrangement of codes of the second grid corresponding to the geographical location; and appending the hierarchical arrangement of codes of the second grid corresponding to the geographical location to the name of the second grid to form a second address of the geographical location.
A yet further aspect of the invention involves a method of addressing a geographical location using a nested grid structure of a geographic referencing system, the nested grid structure including one or more local city grids nested with one or more regional grids. The method includes providing a geographic location; determining a grid which corresponds to the geographical location, the grid including at least one of the one or more local city grids and the one or more regional grids; determining a hierarchical arrangement of codes of the grid corresponding to the geographical location; and appending the hierarchical arrangement of codes of the grid corresponding to the geographical location to the name of the grid to form an address of the geographical location. In a preferred implementation of this method, the type of address generated, local or regional, may depend on user preference.
Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings.